|  | 4.2 | Network Design Methodology
| 4.2.3 | Physical topologies used in networking
After determining the overall requirements for the network, the next step is to decide on an overall LAN topology that will satisfy the user requirements. In this curriculum, we concentrate on the star topology and extended star topology. As you have seen, the star/extended star topology uses Ethernet 802.3 carrier sense multiple access collision detect (CSMA/CD) technology. The reason that this curriculum focuses on a CSMA/CD star topology is that it is by far the dominant configuration in the industry. The major pieces of a LAN topology design can be broken into three unique categories of the OSI reference model-the network layer, the data link layer, and the physical layer. These components are discussed in the following sections.